Make the brittle: Put sugar, syrup, water, and salt in a pot and bring to a boil, then cut back to a simmer. Stir frequently until a caramel has formed. Remove from the heat and fold in the butter, then add the baking soda and pistacchios and stir vigorously. The baking soda will make the mixture bubble. make sure you cook it until it becomes thick. If it is too watery, it won't harden properly. Transfer to a sprayed baking sheet. Spray a rubber spatula to remove from the pot and spread evenly in the pan. Let cool at least 1 hour. Then, cut or break into pieces for service.
make the caramel for the flan: Mix the first batch of sugar in the raw and water, bring to a boil, then cut to a simmer. Simmer until it becomes syrupy. about 3 minutes in, add 1/2 of the lemon zest and juice.
In a large bowl, whisk the egg yolks and sugar. Whisk until it thickens. Add in the lemon juice and vanilla. Continue whisking. Add in the coconut milk and cream a little at a time. If it starts to look too thin, stop adding liquid.
Spray oven proof crocks or ramekins with pan spray. Put them in a baking pan with sides that go at least half way up the sides of the crocks. Pour a short layer of the caramel in the bottom of each ramekin. Save out the citrus zest for garnish. Add in the coconut milk custard in equal portions. Put water in the pan between the crocks and put in a preheated 350 degree oven.
Bake for about 45 minutes to 1 hour, until the flans are firm. They should not jiggle when shaken.
Allow the flans to cool overnight. Then, carefully, run a paring knife around the perimeter of the flans to loosen. Place a plate over the flan and then turn it over. The flan should pop out and be surrounded by a pool of caramel. Garnish with lemon zest, mint, and pistachio brittle and serve. You may need to heat the bottom of the crock to loosen the caramel. This can be done in the microwave.